The proposed research project is concerned with the functions, biosynthesis, genetic specification and control of the thylakoid membrane polypeptides in Chlamydomonas reinhardtii. The functions of the major polypeptides will be ascertained by three complementary approaches. (1) Mutants with specific lesions in the photosynthetic electron transport pathway will be isolated and characterized and any changes in the membrane phenotype will be correlated with the functional lesions. Suppressed derivatives will be obtained to see whether there is a parallel recovery of the altered polypeptides and the deleted functions. (2) Monospecific antibodies to purified polypeptides will be raised and the effects of these antibodies on the various partial photochemical reactions will be examined in order to localize their sites of action. (3) Polypeptides specifically associated with pigments will be identified by isolating discrete chlorophyll-protein complexes from SDS membrane extracts. To investigate the specification and regulation of membrane polypeptides genetic analysis will be carried out with the membrane mutants. Complementation analysis of mutants with identical phenotype will help to determine the number of genes involved in the synthesis and assembly of membrane polypeptides. Attempts will be made to identify structural genes by analysis of heterozygous diploids, by comparing tryptic maps of the polypeptide from wild-type and suppressed strain, and by analysis of mutant polypeptides selected by monospecific antibodies. Mutagens with known specificity for prokaryotic DNA will be used to induce uniparental mutants with membrane defects. Such mutants are useful in defining the role of chloroplast DNA in the biogenesis of thylakoid membranes.